Some working machines, such as large-scale hydraulic excavators and other construction machines, operating in, for example, mines are required to operate 24 hours a day, 365 days a year, substantially without stopping. This makes it necessary to maintain the machine in best possible conditions through a preventive maintenance procedure before the machine is unusually stopped. In general, specialized service personnel perform an inspection through a periodic inspection service procedure to check for possible faulty spots; if a fault is identified, necessary service procedures are performed to maintain the machine in good operating conditions.
Meanwhile, to perform the inspection service procedure, the machine needs to be stopped. For an operator who wants to keep the machine running continuously, the inspection service procedure can be a hindrance to operation if the machine is kept in a good operating condition.
Fault diagnostic techniques have therefore been developed for monitoring operation to identify possible faults by measuring states of the machine using a various types of sensors. A fault diagnostic technique may be used to detect a fault before a machine stop occurs to thereby take preventive measures at early stages, so that a machine failure can be prevented from occurring.
Patent Documents 1 and 2, for example, disclose conventional fault diagnostic techniques. The fault diagnostic technique disclosed in Patent Document 1 derives and identifies a relationship between control command values and various sensor values as a static characteristic function and a boundary function which includes dynamic values, and determines a fault in actual operations using the static characteristic function and the boundary function. The fault diagnostic technique disclosed in Patent Document 2 creates a self-organized map by inputting a sensor value and a differential value thereof and, in actual operations, uses the self-organized map to recognize operation of a construction machine.